Development of aptamer surface-enhanced Raman spectroscopy sensor based on Fe3O4@Pt and Au@Ag nanoparticles for the determination of acetamiprid.

As a common chlorinated nicotinic pesticide with high insecticidal activity, acetamiprid has been widely used for pest control. However, the irrational use of acetamiprid will pollute the environment and thus affect human health. Therefore, it is crucial to develop a simple, highly sensitive, and rapid method for acetamiprid residue detection. In this study, the capture probe (Fe3O4@Pt-Aptamer) was connected with the signal probe (Au@DTNB@Ag CS-cDNA) to form an assembly with multiple SERS-enhanced effects. Combined with magnetic separation technology, a SERS sensor with high sensitivity and stability was constructed to detect acetamiprid residue. Based on the optimal conditions, the SERS intensity measured at 1333 cm-1 is in relation to the concentration of acetamiprid in the range 2.25 × 10-9-2.25 × 10-5 M, and the calculated limit of detection (LOD) was 2.87 × 10-10 M. There was no cross-reactivity with thiacloprid, clothianidin, nitenpyram, imidacloprid, and chlorpyrifos, indicating that this method has good sensitivity and specificity. Finally, the method was applied to the detection of acetamiprid in cucumber samples, and the average recoveries were 94.19-103.58%, with RSD < 2.32%. The sensor can be used to analyse real samples with fast detection speed, high sensitivity, and high selectivity.

Spraying or fertigation? looking for the better method in terms of the lower concentration of Pb and Ni in greenhouse cucumber.

This study was conducted to investigate the status of Lead (Pb) and Nickel (Ni) in greenhouse cucumber affected by fertigation and spraying as a factorial split plot arrangement based on a randomized complete block design (RCBD) with three replications at Soil and Water Research Institute, Karaj, Iran in 2023. The main and sub-plots were respectively fertigation and spraying that was applied in two levels [the minimum permissible concentration of these metals in granular triple super phosphate fertilizer (five ppm Pb and five ppm Ni) as the control treatment, and the maximum permissible concentration of Pb and Ni in granular triple super phosphate fertilizer (50 ppm Pb and 100 ppm Ni)]. Spraying was done in three modes (spraying leaves, leaves + fruit, and fruit). Based on the results, the highest concentration of Pb in the fruit (fruit peel + fruit flesh) (0.295 mg/kg DW) was recorded in the fertigation + spraying with the maximum permissible concentrations of Pb and Ni treatments. A general comparison between the two fertilization methods showed that the spraying method accumulated a higher concentration of Pb in the fruit (i.e., peel + flesh) than the fertigation method. The reverse of this status happened for Ni, so the fertigation method accumulated a higher concentration of Ni in the fruit (skin + flesh) compared to the spraying method. On average, the order of Pb concentration in different organs was as follows: leaf (0.765 mg/kg) > fruit peel (0.232 mg/kg) > fruit peel + flesh (0.174 mg/kg) > fruit flesh (0.129 mg/kg). This order for Ni was as follows: fruit flesh (0.597 mg/kg) > fruit peel + flesh (0.345 mg/kg) > leaf (0.3 mg/kg) > fruit peel (0.175 mg/kg). These orders show that the status of the heavy metals in plant tissues is related to the nature of the metal, the type of the organ, and the method of fertilization.

Red cabbage extract immobilized in bacterial cellulose film as an eco-friendly sensor to monitor microbial contamination and gamma irradiation of stored cucumbers.

The aim of the present study is to develop a pH-sensing biopolymer film based on the immobilization of red cabbage extract (RCE) within bacterial cellulose (BC) to detect contamination and gamma radiation exposure in cucumbers. The results obtained show a sensitivity to pH changes for RCE in its aqueous form and that incorporated within BC films (RCE-BC), both showed color change correlated to bacterial growth (R2 = 0.91), this was supported with increase in pH values from 2 to 12 (R2 = 0.98). RCE and RCE-BC exposure to gamma radiation (0, 2.5, 5, 10, 15, 20, 25 kGy) resulted in gradual decrease in color that was more evident in RCE aqueous samples. To sense bacterial contamination of cucumbers, the total count was followed at 0, 5, 10 and 15 days in cold storage conditions and was found to reach 9.13 and 5.47 log cfu/mL for non-irradiated and 2 kGy irradiated samples, respectively. The main isolates detected throughout this storage period were identified as Pseudomonas fluorescens, Erwinia sp. Pantoea agglomerans using matrix assisted laser desorption ionization-time of flight-ms (MALDI-TOF-MS). Bacterial growth in stored irradiated cucumbers was detected by color change within 5 and 10 days of storage, after which there was no evident change. This is very useful since contamination within the early days of storage cannot be sensed with the naked eye. This study is the first to highlight utilizing RCE and RCE-BC as eco-friendly pH-sensing indicator films for intelligent food packaging to detect both food contamination and gamma preservation for refrigerator stored cucumbers.

Dissipation behaviour and dietary risk evaluation of pesticides on cucumber.

Cucumber (Cucumis sativus L.) is the world's most widely consumed salad vegetable, and it is frequently treated with pesticides to prevent pest and disease outbreaks. Pesticide residues in food commodities impede trade and pose a major health risk. Prior to residue estimation, the QuEChERS approach was validated utilising criteria such as limit of detection, limit of quantitation, linearity, accuracy, and precision. The residues of carbendazim, cypermethrin, ethion, profenofos, quinalphos, and triazophos were examined using a Gas Chromatograph equipped with an Electron Capture Detector or a Flame Photometric Detector and a high-performance liquid chromatography coupled to a photo diode array. The initial deposits of carbendazim, cypermethrin, ethion, profenofos, quinalphos, and triazophos at the prescribed dose were 1.235, 0.407, 0.817, 0.960, 0.628, and 0.985 mg/kg, respectively, with a pre-harvest interval of 5.58-11.30 days. According to the consumer risk evaluation data, the Hazard Quotient is less than one, and the Theoretical Maximum Dietary Intake is less than the Maximum Permissible Intake and Maximum Residue Limit, both of which are considered safe for human consumption at the authorised dose.

Risk Assessment of Pesticide Residues by GC-MSMS and UPLC-MSMS in Edible Vegetables.

In recent years, there has been a significant increase related to pesticide residues in foods, which may increase the risks to the consumer of these foods with the different quality and concentrations of pesticide residues. Pesticides are used for controlling pests that reduce yields. On the other hand, it has become a major public health concern due to its toxic properties. Thus, the objective of the current study employed the application of Quick Easy Cheap Effective Rugged Safe (QuEChERS) method, in combination with gas and liquid chromatography-tandem mass spectrometric detection (GCMSMS, LCMSMS) in order to determine 137 pesticide residues (63 insecticides, 41 acaricides, 40 herbicide, 55 fungicide, nematicide, growth regulator, Chitin synthesis inhibitors, and Juvenile hormone mimics), in 801 vegetables such as 139 tomatoes, 185 peppers, 217 squash, 94 eggplants, and 166 cucumbers from different locations in Hail and Riyadh cities. The results showed that the majority of pesticide residues were detected for each of the following pesticides: acetaimpride, metalaxyl, imidaclopride, bifenthrin, pyridaben, difenoconazole, and azoxystrobien, which were repeated in the samples studied 39, 21, 11, 10, 8, 7, and 5, respectively. In addition, results observed that the tomato was the most contaminated with pesticide residues; it was contaminated with 19 compounds and was followed by pepper, cucumber, and squash, and the last commodity in the contaminated ranking was eggplant. The highest calculated estimated daily intakes (EDIs) were recorded for tomatoes which were estimated between 0.013 to 0.516 mg/kg of body weight per day (bw/day) while the lowest EDIs value was between 0.000002 to 0.0005 mg/kg of bw/day for cucumber. Results indicated that the EDIs values were lower than the acceptable daily intake (ADI) values. Results observed that the most of pesticide residues exposure in food consumption in Saudi Arabia were lower than ADIs. In addition, the highest value for health risk index (HRI) was recorded with Ethion residue in tomato, but in sweet pepper, the highest value for HRI was 127.5 in the form of fipronil residue. On the other hand, results found that the highest values of HRI were 1.54, 1.61, and 0.047 for difenoconazole, bifenthrin, and pyridaben residues in squash, eggplant, and cucumber.

Dissipation and gas chromatographic method for the determination of profenofos residues in/on green pea and cucumber.

Herein we report a novel, accurate and cost-effective gas chromatography method for the determination of average deposits of profenofos on green pea and cucumber following good agricultural practices. Additionally the risk assessment, dissipation and waiting period for profenofos were determined. The average initial deposits (2 h after spraying) of profenofos in/on green pea and cucumber were 3.41 and 3.62 mg kg-1 respectively following two applications at a 10 day interval of profenofos 50EC formulation. Profenofos residues on both of the substrates were below the detection limit of 0.05 mg kg-1 after 20 days at the recommended dosage. For risk assessment studies, the 20th day will be safe for consumers for consumption of green peas. The gas chromatography method was validated according to the SANTE guidelines using the various analytical parameters: linearity, accuracy, detection and quantification limits. The developed method is simple, selective and repeatable and can be extended for profenofos-based standardization of pesticide formulations for green pea/cucumber and their use as pesticides.

Simultaneous determination of the herbicide bixlozone and its metabolites in plant and animal samples by liquid chromatography-tandem mass spectrometry.

Tracing the herbicide bixlozone and its metabolites in food is necessary to assess their risks to human health. In the study, a rapid and effective analytical method using the quick, easy, cheap, effective, rugged, and safe method for the simultaneous determination of bixlozone and its metabolites (2,4-dichlorobenzoic acid, 3-hydroxy-propanamide-bixlozone, and 5'-hydroxy-bixlozone) in plant and animal samples (tomato, cucumber, apple, wheat flour, meat, milk, and egg) was developed based on ultra high performance liquid chromatography-tandem mass spectrometry. The method was validated based on the linearity (R2  > 0.99), sensitivity (limit of quantification = 0.01 mg/kg), recovery (70.2-115.1%), and precision (intraday 1.2-17.6%, interday 0.3-16.0%). Detection was achieved within 6.0 min. The method is reliable for the determination of four target compounds in all seven matrices. The satisfactory validation criteria and successful application show that the proposed methodology is suitable for the detection of four target compounds in real matrices.

A rapid liquid chromatography-electrospray ionization-ion mobility spectrometry method for monitoring nine representative metabolites in the seedlings of cucumber and wheat.

A fast and convenient high-performance liquid chromatography-electrospray ionization-ion mobility spectrometry method was developed to determine nine representative metabolites in the seedlings of cucumber and wheat. The analytical conditions were obtained by optimizing the parameters of high-performance liquid chromatography and ion mobility spectrometry. Briefly, acetonitrile-0.1% formic acid solution was selected as the mobile phase for gradient elution at a flow velocity of 0.4 mL/min. Under negative electrospray ionization mode, spray voltage of ion mobility spectrometry was 4.5 kV, and drift tube temperature was set at 90°C. The metabolites from seedling leaves were extracted using 80% acetonitrile as the solvent at 4°C for 12 h. Results showed that under soilless culture conditions, the contents of maltose, citric acid, and p-hydroxybenzoic acid in the seedlings of cucumber and wheat were reduced by low concentration of itaconic acid, succinic acid, and citric acid. Importantly, this analytical approach demonstrated high sensitivity, good linear response, and high selectivity. The lowest limit of detection was 0.004 µg for p-hydroxybenzoic acid. Overall, this high-performance liquid chromatography-electrospray ionization-ion mobility spectrometry method is sensitive and efficient for rapid separation and identification of plant metabolites.

Time Evolution of Microbial Composition and Metabolic Profile for Biogenic Amines and Free Amino Acids in a Model Cucumber Fermentation System Brined with 0.5% to 5.0% Sodium Chloride.

Salt concentrations in brine and temperature are the major environmental factors that affect activity of microorganisms and, thus may affect formation of biogenic amines (BAs) during the fermentation process. A model system to ferment cucumbers with low salt (0.5%, 1.5% or 5.0% NaCl) at two temperatures (11 or 23 °C) was used to study the ability of indigenous microbiota to produce biogenic amines and metabolize amino acid precursors. Colony counts for presumptive Enterococcus and Enterobacteriaceae increased by 4 and up to 2 log of CFU∙mL-1, respectively, and remained viable for more than 10 days. 16S rRNA sequencing showed that Lactobacillus and Enterobacter were dominant in fermented cucumbers with 0.5% and 1.5% salt concentrations after storage. The initial content of BAs in raw material of 25.44 ± 4.03 mg∙kg-1 fluctuated throughout experiment, but after 6 months there were no significant differences between tested variants. The most abundant BA was putrescine, that reached a maximum concentration of 158.02 ± 25.11 mg∙kg-1. The Biogenic Amines Index (BAI) calculated for all samples was significantly below that needed to induce undesirable effects upon consumption. The highest value was calculated for the 23 °C/5.0% NaCl brine variant after 192 h of fermentation (223.93 ± 54.40). Results presented in this work indicate that possibilities to control spontaneous fermentation by changing salt concentration and temperature to inhibit the formation of BAs are very limited.

Gas chromatography-mass spectrometry-based metabolomics analysis of metabolites in commercial and inoculated pickles.

BACKGROUND: Starter cultures are nowadays more and more used to make inoculated pickles (IPs), but it remains unclear whether there are differences in flavors between IPs and naturally fermented pickles. In this study 16 commercial pickles (CPs) produced by spontaneous fermentation method were purchased from markets in Sichuan province and Chongqing. Ten strains of three lactic acid bacteria species - Lactobacillus plantarum, Leuconostoc mesenteroides and Pediococcus ethanolidurans - were selected as single starter cultures to produce IPs. RESULTS: Differences in flavor components between the CPs and IPs were monitored using a combination of gas chromatography-mass spectrometry and multivariate statistical methods. Higher levels of nonvolatile substances such as glucose, fructose, tagatose, sucrose, lactic acid and mannitol were detected in most IPs than in the CPs. The values of flavor characteristics such as sweetness, umami and astringency, which were correlated positively with consumers' overall preferences for pickles, were higher in the IPs than in the CPs. Volatile compounds such as geranyl acetate, dimethyl trisulfide, eucalyptol and linalool were distinguished as the main compounds that contributed to the flavor characteristics of the CPs. In addition to dimethyl trisulfide, dimethyl disulfide was also an odor contributor to the IPs. CONCLUSIONS: The CPs and IPs had different flavor characteristics, especially in the composition and content of volatile components, and the inoculation method reflected some fermentation advantages, which could reduce the bitterness and increase umami and lead to a higher score of sensory preference. This will be helpful for industrial production. © 2020 Society of Chemical Industry.

Cucumis sativus extract elicits chloride secretion by stimulation of the intestinal TMEM16A ion channel.

CONTEXT: Cucumber (Cucumis sativus Linn. [Cucurbitaceae]) is widely known for its purgative, antidiabetic, antioxidant, and anticancer therapeutic potential. However, its effect on gastrointestinal (GI) disease is unrecognised. OBJECTIVE: This study investigated the effect of C. sativus fruit extract (CCE) on intestinal chloride secretion, motility, and motor function, and the role of TMEM16A chloride channels. MATERIALS AND METHODS: CCE extracts were obtained from commercially available cucumber. Active fractions were then purified by HPLC and analysed by high resolution mass spectrometry. The effect of CCE on intestinal chloride secretion was investigated in human colonic T84 cells, ex vivo mouse intestinal tissue using an Ussing chamber, and the two-electrode voltage-clamp technique to record calcium sensitive TMEM16A chloride currents in Xenopus laevis oocytes. In vivo, intestinal motility was investigated using the loperamide-induced C57BL/6 constipation mouse model. Ex vivo contractility of mouse colonic smooth muscles was assessed by isometric force measurements. RESULTS: CCE increased the short-circuit current (ΔIsc 34.47 ± µA/cm2) and apical membrane chloride conductance (ΔICl 95 ± 8.1 µA/cm2) in intestinal epithelial cells. The effect was dose-dependent, with an EC50 value of 0.06 µg/mL. CCE stimulated the endogenous TMEM16A-induced Cl- current in Xenopus laevis oocytes. Moreover, CCE increased the contractility of smooth muscle in mouse colonic tissue and enhanced small bowel transit in CCE treated mice compared to loperamide controls. Mass spectrometry suggested a cucurbitacin-like analogue with a mass of 512.07 g/mol underlying the bioactivity of CCE. CONCLUSION: A cucurbitacin-like analog present in CCE activates TMEM16A channels, which may have therapeutic potential in cystic fibrosis and intestinal hypodynamic disorders.

Ratiometric Fluorescent Quantum Dot-Based Biosensor for Chlorothalonil Detection via an Inner-Filter Effect.

A new sensitive sensor for detecting chlorothalonil (CHL) based on the inner-filter effect (IFE) between gold nanoparticles (AuNPs) and ratiometric fluorescent quantum dots (RF-QDs) was developed. Here, RF-QDs were designed by two different color CdTe QDs. Based on the IFE, the AuNPs can quench the fluorescence of the RF-QDs. Because of the electrostatic attraction between protamine (PRO) and the AuNPs, the PRO can restore fluorescence effectively. Papain (PAP) can easily hydrolyze PRO and causes the quench of fluorescence quenching. The addition of CHL can inhibit PAP activity and restore the fluorescent signal. Through the characterization of the structural changes of PAP, the inhibition and mechanism of CHL on PAP activity were studied. The ability of CHL to inhibit PAP activity was evaluated by measuring the fluorescence of the RF-QDs. Under the optimal conditions, this sensing platform shows a response to CHL in the range of 0.34-2320 ng/mL and a detection limit of 0.0017 ng/mL. Based on the CHL inhibition of PAP activity, the RF-QDs showed good selectivity for CHL. The practical application of the proposed system was demonstrated by detecting CHL in food and environmental samples with satisfying results.

The Contribution of Romidepsin to the Herbicidal Activity of Burkholderia rinojensis Biopesticide.

The culture broth of Burkholderia rinojensis strain A396 is herbicidal to a number of weed species with greater observed efficacy against broadleaf than grass weeds. A portion of this activity is attributed to romidepsin, a 16-membered cyclic depsipeptide bridged by a 15-membered macrocyclic disulfide. Romidepsin, which is present in small amounts in the broth (18 to 25 µg mL-1), was isolated and purified using standard chromatographic techniques. It was established that romidepsin is a natural proherbicide that targets the activity of plant histone deacetylases (HDAC). Assays to measure plant HDAC activity were optimized by testing a number of HDAC substrates. The activity of romidepsin was greater when its macrocyclic-forming disulfide bridge was reduced to liberate a highly reactive free butenyl thiol side chain. Reduction was achieved using 200 mM tris(2-carboxyethyl)phosphine hydrochloride. A similar bioactivation of the proherbicide via reduction of the disulfide bridge of romidepsin was observed in plant-cell-free extracts. Molecular dynamic simulation of the binding of romidepsin to Arabidopsis thaliana HDAC19 indicated the reduced form of the compound could reach deep inside the catalytic domain and interact with an associated zinc atom required for enzyme activity.

Monitoring and predicting Fusarium wilt disease in cucumbers based on quantitative analysis of kinetic imaging of chlorophyll fluorescence.

Cucumber (Cucumis sativus L.) is a widely cultivated and economically profitable crop. However, Fusarium wilt disease can seriously affect cucumber yields, as it is difficult to prevent and eliminate. Therefore, a reliable method is needed for the rapid and early detection of Fusarium infection in cucumbers, which could be provided via the kinetic imaging of chlorophyll fluorescence (ChlF). In this study, ChlF imaging and kinetic parameters were utilized with gray and radial basis function models to monitor cucumber Fusarium wilt disease. The results indicate that the disease can be detected and predicted using this imaging technique before symptoms become visible.

Spectrophotometric detection of fenthion in foods after extraction by magnetic zirconia.

A magnetic material, Fe3O4@ZrO2, was used to enrich an organophosphorus pesticide, fenthion. After enrichment the Fe3O4@ZrO2 was treated with NaOH to elute and hydrolyze fenthion. The hydrolysis products, orthophosphate ions, combine to molybdate ions to yield molybdophosphoric acid, which was further reduced with SnCl2 to obtain a blue phosphatemolybdate. The content of orthophosphate ions as well as fenthion can be determined through the spectrophotometric method. Adsorption and elution conditions were optimized to obtain an enrichment factor of 12.5. The proposed composite method was successfully used to analyze the fenthion residues on the skin of cucumber and apple samples. The limit of detection was as low as 0.037 mg/Kg, which was close to that of the gas chromatography-mass spectrometer method. The method was simple, rapid, and economic, suitable for the rapid screen of fenthion and the other organophosphorus pesticide in mass samples.

Influence of salt concentration and iodized table salt on the microbiota of fermented cucumbers.

The fermentation of vegetables is a traditional preservation method, that experiences a renaissance even in domestic households. Table salt is added to the fermentation batches to favor the growth of lactic acid bacteria usually. On an industrial scale, the fermentation brine is typically prepared with non-iodized table salt. In our study, we investigated the microbiota of cucumber fermentations using culture-dependent and -independent methods. We could show that the fermentation process of cucumbers and the involved microbiota is influenced by the concentration of table salt and not by the use of iodized table salt. Therefore, we conclude that the use of iodized table salt does not negatively affect the fermentation process. We could verify that iodine permeates the cucumbers by diffusion, leading to satisfactory iodine concentrations in the final food product. The industrial use of iodized table salt in food fermentations could contribute to maintain a constant iodine supply to the general public.

Content of xylose, trehalose and l-citrulline in cucumber fermentations and utilization of such compounds by certain lactic acid bacteria.

This research determined the concentration of trehalose, xylose and l-citrulline in fresh and fermented cucumbers and their utilization by Lactobacillus pentosus, Lactobacillus plantarum, Lactobacillus brevis and Lactobacillus buchneri. Targeted compounds were measured by HPLC and the ability of the lactobacilli to utilize them was scrutinized in fermented cucumber juice. Fresh cucumber juice was supplemented with trehalose, xylose and l-citrulline to observed mixed culture fermentations. Changes in the biochemistry, pH and colony counts during fermentations were monitored. Trehalose, xylose and l-citrulline were detected in fermentations to15.51 ± 1.68 mM, a fresh cucumber sample at 36.05 mM and in fresh and fermented cucumber samples at 1.05 ± 0.63 mM, respectively. Most of the LAB tested utilized trehalose and xylose in FCJM at pH 4.7. l-citrulline was utilized by L. buchneri and produced by other LAB. l-citrulline (12.43 ± 2.3 mM) was converted to ammonia (14.54 ± 3.60 mM) and the biogenic amine ornithine (14.19 ± 1.07 mM) by L. buchneri at pH 4.7 in the presence of 0.5 ± 0.2 mM glucose enhancing growth by 0.5 log CFU/mL. The use of a mixed starter culture containing L. buchneri aided in the removal of l-citrulline and enhanced the fermentation stability. The utilization of l-citrulline by L. buchneri may be a cause of concern for the stability of cucumber fermentations at pH 3.7 or above. This study identifies the use of a tripartite starter culture as an enhancer of microbial stability for fermented cucumbers.

Effect of Cultivar on Chlorophyll Meter and Canopy Reflectance Measurements in Cucumber.

Optical sensors can be used to assess crop N status to assist with N fertilizer management. Differences between cultivars may affect optical sensor measurement. Cultivar effects on measurements made with the SPAD-502 (Soil Plant Analysis Development) meter and the MC-100 (Chlorophyll Concentration Meter), and of several vegetation indices measured with the Crop Circle ACS470 canopy reflectance sensor, were assessed. A cucumber (Cucumis sativus L.) crop was grown in a greenhouse, with three cultivars. Each cultivar received three N treatments, of increasing N concentration, being deficient (N1), sufficient (N2) and excessive (N3). There were significant differences between cultivars in the measurements made with both chlorophyll meters, particularly when N supply was sufficient and excessive (N2 and N3 treatments, respectively). There were no consistent differences between cultivars in vegetation indices. Optical sensor measurements were strongly linearly related to leaf N content in each of the three cultivars. The lack of a consistent effect of cultivar on the relationship with leaf N content suggests that a unique equation to estimate leaf N content from vegetation indices can be applied to all three cultivars. Results of chlorophyll meter measurements suggest that care should be taken when using sufficiency values, determined for a particular cultivar.

Meptyldinocap and azoxystrobin residue behaviors in different ecosystems under open field conditions and distribution on processed cucumber.

BACKGROUND: Several diseases and insects may cause damage to the normal growth of cucumber. Azoxystrobin and meptyldinocap, because of their novel mode of action, are effective against pathogens that have developed reduced sensitivity to other fungicides. Azoxystrobin is persistent in various crops and environments. However, there is a lack of research on the dissipation of these two pesticides, especially meptyldinocap. RESULTS: Analytes could be quantified with decent recoveries of 90-101%, with relative standard deviations (RSDs) of 3.0-10.1%. The terminal residues of meptyldinocap and azoxystrobin in cucumber were all < limit of quantification (LOQ) (0.02 and 0.05 mg kg-1 ). The half-lives of meptyldinocap and azoxystrobin were 0.8-1.1 and 1.2-2.8 days, respectively. The processing factors (PFs) for washing were all < 1, but the removal rate for washing was < 29.0%. Peeling had a significant effect on the removal of pesticide. The largest residue reductions were noticed through the pickling process, but special care should be taken regarding residues in the pickling solution as pesticides could transfer to them from cucumber. A more interesting finding was that the degradation of two pesticides was accelerated by the addition of calcium oxide. CONCLUSION: Pesticide residues on cucumber decreased after these processes. These results enable the health-risks from dietary exposures to pesticide residues to be characterized. They enable maximum residue limits (MRLs) to be established for pesticide residues in food products. They also assist the optimization of food processing with regard to pesticide residue dissipation. © 2019 Society of Chemical Industry.

Dissipation, residues and risk assessment of pyraclostrobin and picoxystrobin in cucumber under field conditions.

BACKGROUND: Pyraclostrobin and picoxystrobin are two representative pesticides of strobilurins used to treat cucumber downy mildew, which have raised issues of food safety and human health. A new formulation containing these two compounds is being prepared for marketing in China. RESULTS: The dissipation and residual levels of pyraclostrobin and picoxystrobin in cucumbers under field conditions were determined simultaneously by a validated method via liquid chromatography-tandem mass spectrometry (LC-MS/MS). The dissipation rules were described by first-order kinetics and the half-lives of pyraclostrobin and picoxystrobin were less than 8.2 days and 3.4 days. The highest terminal residue of pyraclostrobin was 0.014 mg kg-1 which was lower than maximum residue limit (MRL) in China (0.5 mg kg-1 ) and of picoxystrobin was 0.029 mg kg-1 , respectively. In the long-term intake risk assessment of pyraclostrobin and picoxystrobin for general population (18-79 years), the chronic risk quotient (RQc ) varied from 5.64% to 21.97%. The assessment of short-term risks included children (1-6 years) and adults (18-79 years) and in which the RQa values were 0.38% and 2.85%. Both results showed the intake risks of cucumber were acceptable. CONCLUSION: Pyraclostrobin and picoxystrobin degraded easily in cucumbers under open field conditions. The long-term and short-term risks caused by final residues of pyraclostrobin and picoxystrobin were insignificant. The recommended pre-harvest interval of 3 days was safe. The article will be helpful in rational use of these pesticides and MRL formulation of picoxystrobin on cucumber. © 2020 Society of Chemical Industry.